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Convective/Storm Discussion Thread - 1st August onwards


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Despite just having very heavy rain, I witnessed at about 02:30-3AM some of the best distant lightning I've ever seen, coupled with some real deep low bass sounding rumbles! 

Absolutely astonishing that it's only April as others have said. This event alone was better than probably every summer from the years 2007-11. Remarkable. 

This did remind me of a pretty good storm one April in 2004-05 time, that's the only other time I can remember a night storm in April. 

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My contribution to this evening.

What a fantastic night we had in central southern England, and many other places too! I've never seen storms of that intensity or frequency in April before! Anyway I thought I would share so

Posted Images

1 hour ago, Nick F said:

Storm & Convective Forecast

stormmap_220418.thumb.png.8597d2b60c20c6d85750c6d066e6d556.png

Issued 2018-04-21 21:54:57
Valid: 22/04/2018 0600z - 23/04/2018 0600z

THUNDERSTORM OUTLOOK - DAY 1 (SUN 22ND APRIL)

Synopsis

During Sunday, occluding cold front moving east ahead of low moving NE between Iceland and Scotland will bring a band of cloud and rain across country with cooler and more stable conditions of Atlantic origin following. However, warm, humid and unstable airmass will hang on across SE England and E Anglia into the afternoon, - which may trigger isolated thunderstorms with surface heating.

DAY 1 THUNDERSTORM OUTLOOK

VALID: 22/0600Z - 23/0600Z

... SE ENGLAND and E ANGLIA ...

*Risk of ...

Hail (isolated large), flash-flooding, gusty winds and frequent lightning

Warm and humid airmass ahead of cold front moving in from the west will become unstable with surface heating in sunny spells aided by continued cooling aloft steepening lapse rates, surface breeze convergence ahead of approaching front the west combined with large scale ascent of approaching upper trough may support the development of a few thunderstorms with peak heating in the afternoon, provided there is some sunshine. 30-40 knots of deep layer shear, strong SWLy flow aloft and 300-600 j/kg CAPE may allow storms to organise, perhaps strong enough to bring some isolated large hail, localised flash flooding, gusty winds and with LCLs lower than today, a brief funnel or weak tornado can't be ruled with storms forming or crossing along wind shift.

Issued by: Nick Finnis

Hi Nick. Just curious as to why no tornado symbol as it was mentioned in the forecast?

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29 minutes ago, Summer Sun said:

No rain at all here in Darlo missed the lot of it

The MDT zone was pretty accurate further south

 

I love ConvectiveWeather but whilst the forecast was accurate for many areas, they moved the MDT zone westwards after we had received all our lightning across Bristol, Bath into Wiltshire?

Bit like the Met Office as people mentioned, issuing a yellow warning for rain when people already received all their rain and wasn’t getting anymore aha!

Edited by Ben Sainsbury
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Gave up in the end and went to sleep the wine may have played a part in that. I was in a sort of half asleep state when I could here deep rumbling, must have taken a while for me to realise what it was and then I saw a flash through my eyelids. Had a good 15 minutes of fairly frequent lightning and torrential rain.  Absolutely perfect!

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23 minutes ago, Ben Sainsbury said:

I love ConvectiveWeather but whilst the forecast was accurate for many areas, they moved the MDT zone westwards after we had received all our lightning across Bristol, Bath into Wiltshire?

Bit like the Met Office as people mentioned, issuing a yellow warning for rain when people already received all their rain and wasn’t getting anymore aha!

Indeed, here's the evolution of the forecast for Saturday. In general, everything developed about 50 miles further west than earlier expectations, and hence no point keeping a 'wrong' forecast online when nowcasting would suggest the risk had shifted slightly west. 

comp.png

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I found it interesting to observe that last night’s storms seemed to fit into the category of ‘pulse thunderstorms’ - where within mere minutes cells would out of nowhere become like mature summer storms and last for anything up to half an hour, but then they would almost just stop completely - like someone pulled the plug.

I guess that’s what you get when you try and do your MCS storm out-of-season :laugh:

 

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2 minutes ago, Flash bang flash bang etc said:

I found it interesting to observe that last night’s storms seemed to fit into the category of ‘pulse thunderstorms’ - where within mere minutes cells would out of nowhere become like mature summer storms and last for anything up to half an hour, but then they would almost just stop completely - like someone pulled the plug.

I guess that’s what you get when you try and do your MCS storm out-of-season :laugh:

 

Must admit it was unusual and very quick from alto to accas to cumulus to full blown storm  40 mins so pulse might be the case here in the nw .

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2 hours ago, Ben Sainsbury said:

I love ConvectiveWeather but whilst the forecast was accurate for many areas, they moved the MDT zone westwards after we had received all our lightning across Bristol, Bath into Wiltshire?

Bit like the Met Office as people mentioned, issuing a yellow warning for rain when people already received all their rain and wasn’t getting anymore aha!

That isn't strictly true because yes those revised warnings were too late for the early evening storms but some of those same areas then had further severe, quickly developing conditions after midnight.

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1 hour ago, Flash bang flash bang etc said:

I found it interesting to observe that last night’s storms seemed to fit into the category of ‘pulse thunderstorms’ - where within mere minutes cells would out of nowhere become like mature summer storms and last for anything up to half an hour, but then they would almost just stop completely - like someone pulled the plug.

I guess that’s what you get when you try and do your MCS storm out-of-season :laugh:

 

Yep, storms got within spitting distance of here and then all electrical activity just stopped. Didn't even hear so much as a rumble.:angry:

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I think only 30th April 2005 compares to the Lightning activity seen yesterday just east of here in April. 

Pleased to have had two thunder days this month though!

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I want more! Looking at our chances for later today, or even maybe heading east if it all kicks off there...

Yesterday was actually a really useful warm up, as I discovered I’ve hardly got any space left on my phone for photos and I can’t find half my stuff (like my proper big tripod).

Great to have an opportunity to realise this before the Summer season kicks off properly - but another little April surprise would be great to get a little more practice in... :p

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3 hours ago, staplehurst said:

Indeed, here's the evolution of the forecast for Saturday. In general, everything developed about 50 miles further west than earlier expectations, and hence no point keeping a 'wrong' forecast online when nowcasting would suggest the risk had shifted slightly west. 

comp.png

Which is why I suggested radar watching rather than taking convective forecasts as gospel.

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2 hours ago, Andy Bown said:

That isn't strictly true because yes those revised warnings were too late for the early evening storms but some of those same areas then had further severe, quickly developing conditions after midnight.

I understand what you're saying, but did the following storms really warrant a moderate for our area? Whilst there was still some fairly frequent lightning, wasn't anything as significant as what was earlier witnessed. If after the earlier storms passed and someone told me that there was a 45% - 60% of seeing more lightning, I'd be complete and utterly surprised as by that point the favourable conditions were much further east. 

Just my opinion and by good heart, but good to see another side to things.

Criteria.jpg

Edited by Ben Sainsbury
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6 hours ago, Windblade said:

Hi Nick. Just curious as to why no tornado symbol as it was mentioned in the forecast?

Good question, the maps with the symbols is a new concept I'm trying out for the Netweather forecasts, as is the areas depicted, for now only using the tornado symbol if I feel there is good confidence and likelihood of the type of storms that may produce one, confidence is low for this afternoon, so although not ruling out in the forecast, I think to put the symbol on the map would imply confidence of one forming - which there isn't.

To echo Paul's post above, really don't understand the bashing the UK convective forecasts get, forecasting thunderstorms with any detail to where storms will form and where they will affect with any accuracy is inherently difficult - especially the UK, so we rely on models and a little recent obs data, such as radiosonde ascents and station data upstream of areas where storms may form to work out the forecasts, but models can often be out, even at short-range with simulating convection. Often a convective forecast issued in advance will tend have errors in reality to mapping where storms are most likely, but that is unfortunately often a downside for those who produce them, but the forecasts can give a general idea of where storms are most likely and whether they will be isolated, likely, strong or even severe - given parameters shown by models and obs.

 

Edited by Nick F
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39 minutes ago, Paul Sherman said:

It says in your Logo "Amatuer Meteorologist and Storm Forecaster" Ben

Any chance you could put a little effort into a forecast for the next convective event ? It's all too easy to bash others that give their opinions on here. Remember they are forecasting when conditions look favourable with what they have on the table from the models they look at and it did to them warrant a Moderate with 800-1000 MU Cape and an active front coming in from the west.

Like I said hope to see you forecast the next chance of Thunder in the Uk and will look out for it and certainly WONT bash it if it goes wrong - Dan and Convective Weather like Torro and Nick here on Netweather do an amazing job and should be applauded IMHO

He did. I congratulated him on how clearly set out it was.

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15 minutes ago, MP-R said:

He did. I congratulated him on how clearly set out it was.

Ah sorry must have missed it, will trawl back through the pages and have a look - Cheers MPR

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